Provided is a forced-regeneration treatment method for an exhaust-gas aftertreatment device (DPF) and an associated engine-driven compressor. When the amount of particulate matter (PM) deposited in a filter element of a DPF reaches a predetermined amount and a forced-regeneration start command is input, a capacity controlling means of the engine-driven compressor is disabled to close an intake valve and to open the discharge side of a compressor main unit to atmosphere, thereby causing the compressor main unit to achieve a low-load state. The operation mode of the engine is switched to a predetermined forced-regeneration mode to operate the engine at a predetermined speed and to increase the temperature of the gas. The temperature inside the DPF is increased to reach a temperature at which an oxidative catalyst is activated and to a temperature lower than the self-combustion temperature of the PM, thereby forcibly burning the PM.

A fuel injection amount control apparatus comprises an air-fuel ratio sensor disposed between an exhaust gas merging portion and an upstream catalyst. The control apparatus performs a feedback correction on an amount of fuel to be injected by the fuel injection valve so that an air-fuel ratio represented by the output value of the upstream air-fuel ratio sensor becomes equal to a target air-fuel ratio set at stoichiometric air-fuel ratio. The control apparatus obtains an air-fuel ratio imbalance indicating value, which becomes larger as a difference in air-fuel ratio of each of the mixtures supplied to each of the combustion chambers among the cylinders becomes larger, and performs an increasing correction to the instructed fuel injection amount in such a manner that an air-fuel ratio determined by the instructed fuel injection amount becomes richer than the stoichiometric air-fuel ratio as the obtained air-fuel ratio imbalance indicating value increases.

An internally cooled internal combustion piston engine and method of operating a piston engine is provided, with the combination of liquid water injection, higher compression ratios than conventional engines, and leaner air fuel mixtures than conventional engines. The effective compression ratio of the engines herein is greater than 13:1. The engines may employ gasoline or natural gas and use spark ignition, or the engines may employ a diesel-type fuel and use compression ignition. The liquid water injection provides internal cooling, reducing or eliminating the heat rejection to the radiator, reduces engine knock, and reduces NOx emissions. The method of engine operation using internal cooling with liquid water injection, high compression ratio and lean air fuel mixture allow for more complete and efficient combustion and therefore better thermal efficiency as compared to conventional engines.

A control device for an internal combustion engine, said control device implementing a lean control, whereby the air-fuel ratio of the exhaust gas flowing into an exhaust purification catalyst is set to a lean air-fuel ratio setting, and a rich control, whereby the air-fuel ratio of the exhaust gas flowing into the exhaust purification catalyst is set to a rich air-fuel ratio setting. When the amount of oxygen absorbed by the exhaust purification catalyst during lean control reaches or exceeds a criterion storage amount, a control is executed to switch to rich control. In addition, a control is executed to set the lean air-fuel ratio setting for a first intake air amount so as to be richer than the lean air-fuel ratio setting for a second intake air amount that is less than the first intake air amount.

An exhaust purification system of an internal combustion engine which has a plurality of cylinders is comprised of an exhaust purification catalyst, a downstream side air-fuel ratio sensor, and a control device which controls the average air-fuel ratio of the exhaust gas and the combustion air-fuel ratios of the cylinders. The control device performs average air-fuel ratio control where it alternately controls the average air-fuel ratio between the rich air-fuel ratio and the lean air-fuel ratio and inter-cylinder air-fuel ratio control where it controls the combustion air-fuel ratios of the cylinders so that the combustion air-fuel ratio becomes the rich air-fuel ratio at least at one cylinder among the plurality of cylinders even when the average air-fuel ratio is controlled to the lean air-fuel ratio by average air-fuel ratio control. In average air-fuel ratio control, the average air-fuel ratio is controlled so that the lean shift amount when controlling the average air-fuel ratio to the lean air-fuel ratio becomes smaller than the rich shift amount when controlling the average air-fuel ratio to the rich air-fuel ratio.

The internal combustion engine comprises an exhaust purification catalyst able to store oxygen, and a downstream side air-fuel ratio sensor arranged at a downstream side of the exhaust purification catalyst in a direction of exhaust flow. The control system performs feedback control of an amount of fuel fed to a combustion chamber of the internal combustion engine so that an air-fuel ratio of exhaust gas flowing into the exhaust purification catalyst becomes a target air-fuel ratio and performs learning control to correct a parameter relating to the feedback control based on an air-fuel ratio of exhaust gas detected by the downstream side air-fuel ratio sensor. The target air-fuel ratio is alternately switched between a rich set air-fuel ratio and a lean set air-fuel ratio leaner. When a condition for learning acceleration, which is satisfied when it is necessary to accelerate correction of the parameter by the learning control, is satisfied, a rich degree of the rich set air-fuel ratio is increased. Therefore, there is provided an internal combustion engine able to suitably change the speed of updating the learning value.

An internal combustion engine comprises: an exhaust purification catalyst; a downstream side air-fuel ratio sensor which is arranged at a downstream side of the exhaust purification catalyst; and an air-fuel ratio control system which performs feedback control so that the air-fuel ratio of the exhaust gas flowing into the exhaust purification catalyst becomes a target air-fuel ratio. The air-fuel ratio control system switches the target air-fuel ratio to a lean set air-fuel ratio when the air-fuel ratio detected by the downstream side air-fuel ratio sensor becomes a rich judged air-fuel ratio or less; changes the target air-fuel ratio to a slight lean set air-fuel ratio after switching the target air-fuel ratio to the lean set air-fuel ratio and before an estimated value of the oxygen storage amount of the exhaust purification catalyst becomes a switching reference storage amount or more; and switches the target air-fuel ratio to a rich air-fuel ratio when the estimated value of the oxygen storage amount of the exhaust purification catalyst becomes the switching reference storage amount or more.

An internal combustion engine comprises an exhaust purification catalyst arranged in an exhaust passage of the internal combustion engine and being able to store oxygen in inflowing exhaust gas and an air-fuel ratio sensor arranged at a downstream side of the exhaust purification catalyst in a direction of exhaust flow and detecting an air-fuel ratio of exhaust gas flowing out from the exhaust purification catalyst and stops or decreases a feed of fuel to a combustion chamber as fuel cut control. The abnormality diagnosis system calculates a characteristic of change of an air-fuel ratio based on an output air-fuel ratio output from the air-fuel ratio sensor at the time when the output air-fuel ratio first passes a part of an air-fuel ratio region of a stoichiometric air-fuel ratio or more after an end of the fuel cut control, and diagnoses abnormality of the air-fuel ratio sensor based on the characteristic of change of the air-fuel ratio. As a result, the diagnosis system can diagnose the abnormality of deterioration of response of the downstream side air-fuel ratio sensor when necessary without fail when performing fuel cut control.

A system according to the principles of the present disclosure includes a storage capability module and at least one of an engine speed control module and a spark control module. The storage capability module determines a capability of a catalytic converter to store oxygen. The engine speed control module controls a speed of an engine based on the oxygen storage capability of the catalytic converter. The spark control module controls a spark timing of the engine based on the oxygen storage capability of the catalytic converter.

A method of calculating an ammonia (NH3) mass generated in a lean NOx trap (LNT) of an exhaust purification device includes sequentially calculating a NH3 mass flow at a downstream of each slice from a first slice to an n-th slice, and integrating the NH3 mass flow at the downstream of the n-th slice over a predetermined time, wherein the calculation of the NH3 mass flow at the downstream of the i-th slice comprises calculating a NH3 mass flow flowing into the i-th slice, calculating a NH3 mass flow generated at the i-th slice, and adding the NH3 mass flow generated at the i-th slice to a value obtained by subtracting the NH3 mass flow used to reduce the NOx and the O2 at the i-th slice from the NH3 mass flow flowing into the i-th slice.